Deborah Halber, MIT, 617-258-9276,

Roger Sudbury, Lincoln Lab, 781-981-7024,

PASADENA, Calif. — A Massachusetts Institute of Technology researcher said
today (Oct. 24) that the number of near-Earth asteroids (NEAs) may be
higher than recent estimates.

Research presented by MIT graduate student Scott Stuart at a meeting of the
American Astronomical Society’s Division of Planetary Science showed that
because the inclinations — angles of orbit in relation to the plane of the
Earth’s orbit around the sun — of known NEAs are not representative of the
entire population, there may be more undetected NEAs out there.

NEAs with low inclinations are easier to find than highly inclined NEAs,
Stuart noted. Thus, the known NEAs tend to have low inclinations rather
than being representative of the population.

With the new determination of higher inclinations for the NEA population,
researchers at MIT Lincoln Laboratory now estimate that there is a mean
total of more than 1,100 near-Earth asteroids bigger than 1 kilometer (0.6
miles) in diameter. Recent estimates had ranged from 750 to 900. Those
prior estimates used a small number of asteroid detections and assumed that
the NEAs have lower inclinations than suggested by Lincoln Near-Earth
Asteroid Research (LINEAR) Project data.

This new number is consistent with earlier estimates of the population made
by the late astrogeologist Eugene Shoemaker, who based his analysis on the
number of asteroid impact craters on the moon.

NEAs are objects within our solar system whose orbits may bring them close
to the Earth. While no currently known NEAs are now on a collision course
with the Earth, many NEAs remain undetected.

The amount of damage that would be caused by an asteroid depends on its
size. Asteroids bigger than 1 kilometer are thought to be capable of
causing extensive damage on a global scale.

Astronomers find and catalog asteroids by imaging large swaths of sky with
telescopes and searching for objects that move against the background of
fixed stars. By tracking an asteroid’s location over several months,
astronomers can calculate the orbit that the asteroid follows and determine
whether it could pose a hazard to the Earth.

LINEAR has been scanning the skies to discover and catalog NEAs and to
provide advance warning if any are bound for Earth. Since March 1998,
LINEAR has found 70 percent of all near-Earth asteroids discovered
worldwide. It is a major contributor toward NASA’s goal of cataloging 90
percent of NEAs larger than 1 kilometer within the next 10 years.

No one yet knows exactly how many NEAs are out there. However, it is
possible to make estimates of the number remaining to be discovered based
on the number already found and the amount of searching that has been done
to discover them.

LINEAR has detected more than 400 different near-Earth asteroids. This
ten-fold increase in detections has allowed researchers to investigate more
accurately the inclination distribution of NEAs.

Stuart is a participant in the MIT Lincoln Laboratory Scholars program, an
employee education program, working with Richard Binzel, professor of
Earth, Atmospheric and Planetary Sciences at MIT, and a member of the
LINEAR project team. Principal investigator of the LINEAR project at
Lincoln Laboratory is Grant Stokes, assistant division head.

The LINEAR project, conducted by MIT Lincoln Laboratory, is jointly
sponsored by NASA and the United States Air Force under contract number

“Opinions, interpretations, conclusions, and recommendations are those of
the author and are not necessarily endorsed by the United States Air Force.”